1. Field of the Invention
The present invention relates to a torque detector.
2. Background Information
In order to conduct a characteristic evaluation of a rotation powertrain of a vehicle, a test using a torque detector in which torque measurement of the rotation powertrain is conducted is necessary. The torque detector is formed of a rotary shaft and a plurality of strain gages attached to a surface of a torque detecting portion of the rotary shaft. Respective strain gages form resistors of a resistance bridge circuit in a torque arithmetic portion. The strain gages detect the magnitude of shear stress generated on the surface of the rotary shaft due to torque applied to the rotary shaft. The torque arithmetic portion converts the magnitude of change of the output voltage appearing in the resistance bridge circuit with respect to the input voltage to torque.
In order to detect torque by using one torque detector, the detector needs to include a torque detecting portion adapted for maximum torque. In this case, the accuracy of small torque detection is reduced. Therefore, in order to detect accurately a small torque, it is necessary to prepare a plurality of torque detecting portions and to change the torque detecting portion for every measurement. However, changing the operation of the torque detection portion is complicated and reduces the operation efficiency of the test.
In view of the above, there exists a need for a torque detector that overcomes the above mentioned problems in the prior art. This invention addresses this need in the prior art as well as other needs, which will become apparent to those skilled in the art from this disclosure.
It is an object of the present invention to make it possible to detect efficiently and accurately small torque.
A torque detector according to a first aspect of the present invention has, a first torque detecting portion, a first torque sensor, a second torque detecting portion, and a second torque sensor. The first torque sensor is provided on the first torque detecting portion to detect torque. The second torque detecting portion has lower rigidity than the first torque detecting portion. The second torque sensor is provided to the second torque detecting portion and detects torque that is smaller than the torque detected by the first torque sensor. In the torque detector, the second torque sensor detects small torque and the first torque sensor detects large torque. Therefore, it is unnecessary to change the torque detecting portion, and it is possible to detect efficiently and accurately small torque.
A torque detector according to a second aspect of the present invention is a torque detector of the first aspect and further includes a stopper portion. The stopper portion stops torsional operation of the second torque detecting portion when a predetermined torsion angle is obtained. In the torque detector of the second aspect, if the torsion angle reaches a predetermined angle, the stopper portion stops the torsional operation of the second torque detecting portion and torque is not transmitted thereafter by the second torque detecting portion. In other words, the second torque detecting portion is protected while the large torque is detected by the first torque detecting portion.
A torque detector according to a third aspect of the present invention has a first torque detecting portion, a first torque sensor, a second torque detecting portion, a second torque sensor, and a stopper portion. The first torque sensor is provided for the first torque detecting portion to detect torque. The second torque detecting portion is disposed to operate in series with the first torque detecting portion in a rotating direction and has a lower rigidity than the first torque detecting portion. The second torque sensor is provided for the second torque detecting portion and detects smaller torque than the first torque sensor detects. The stopper portion is disposed to operate in parallel with the second torque detecting portion in the rotating direction. The stopper portion stops torsional operation of the second torque detecting portion when a predetermined torsion angle is obtained.
In the torque detector of the third aspect, the second torque detecting portion is twisted, and the second torque sensor detects small torque in a small torsion angle region. When the torsion angle reaches the predetermined angle, the stopper portion stops the torsional operation of the second torque detecting portion. Torque is thereafter transmitted through the stopper portion allowing the first torque sensor to detect large torque with the first torque detecting portion.
In the torque detector of the third aspect, the second torque sensor detects small torque and the first torque sensor detects large torque. Therefore, it is unnecessary to change the torque detecting portion and it is possible to detect small torque efficiently and accurately. The second torque detecting portion is protected by the stopper portion while the large torque is detected by the first torque detecting portion.
A torque detector according to a fourth aspect of the present invention has a first member, a first torque sensor, a second torque sensor, a second member, and a stopper portion. The first member includes a first torque detecting portion and a second torque detecting portion. The second torque detecting portion operates in series with the first torque detecting portion in a rotating direction and has a lower rigidity than the first torque detecting portion. The first torque sensor is provided for the first torque detecting portion. The second torque sensor is provided for the second torque detecting portion to detect torque smaller than that which the first torque sensor detects. The second member is disposed close to the first member. The stopper portion is disposed in parallel with the second torque detecting portion in the rotating direction. The stopper portion is arranged to transmit torque between the second member and the first torque detecting portion. The stopper portion is also arranged to prevent transmission of torque until a predetermined torsion angle is obtained.
In the torque detector of the fourth aspect, if the first member rotates, for example, torque of the first member is transmitted to the second member through the first torque detecting portion and the second torque detecting portion of the first member. The second torque sensor detects small torque with the second torque detecting portion in a region of a small torsion angle. When the torsion angle reaches the predetermined angle, the stopper portion starts torque transmission. In other words, torque of the first member is transmitted to the second member through the first torque detecting portion and then to the first torque transmitting portion, preferably in that order. The first torque sensor thereby detects large torque with the first torque detecting portion.
In the torque detector, the second torque sensor detects small torque and the first torque sensor detects large torque. Therefore, it is unnecessary to change the torque detecting portion, and it is possible to detect small torque efficiently and accurately. The second torque detecting portion is protected by the stopper portion while the large torque is detected in the first torque detecting portion.
In a torque detector according to a fifth aspect of the present invention, the second torque detecting portion of the torque detector of the fourth aspect has an elastic member which can be contracted in the rotating direction between the first member and the second member.
In a torque detector according to a sixth aspect, the torque detector of the fifth aspect is arranged so that initial torque is applied to the elastic member.
In this torque detector, the elastic member is not contracted in the rotating direction until torsional torque exceeds the initial torque of the elastic member. In other words, the first member and the second member rotate together and frictional resistance is not generated between both the members until that time. As a result, the second torque sensor can accurately detect minute torque.
A torque detector according to a seventh aspect includes a first member, a first torque sensor, a second torque sensor, a second member, and a stopper portion. The first torque sensor is provided for the first torque detecting portion. The second torque sensor is provided for the second torque detecting portion and is configured to detect smaller torque than the torque for which the first torque sensor is configured. The first member includes a shaft-shaped first torque detecting portion, a second torque detecting portion, and a flange. The second torque detecting portion is provided on a tip end of the first torque detecting portion and has a lower rigidity than the first torque detecting portion. The flange is formed between the first torque detecting portion and the second torque detecting portion. The second member is connected in a rotating direction to the first member through the second torque detecting portion. The stopper portion is formed between the second member and the flange to prevent transmission of torque until a torsion angle between the first member and the second member reaches a predetermined angle.
In this torque detector, if the first member rotates with respect to the second member, the second torque sensor detects small torque with the second torque detecting portion in a small torsion angle region. When the torsion angle reaches the predetermined angle, torque transmission is started by the stopper portion and torsional operation of the second torque detecting portion is stopped. In other words, torque is thereafter transmitted through the stopper portion and the first torque sensor detects large torque with the first torque detecting portion.
In this torque detector, the second torque sensor detects small torque and the first torque sensor detects large torque. Therefore, it is unnecessary to change the torque detecting portion and it is possible to detect small torque efficiently and accurately. The second torque detecting portion is protected by the stopper portion while the large torque is detected in the first torque detecting portion.
In a torque detector according to an eighth aspect, the second torque detecting portion of the torque detector of the seventh aspect has an elastic member which can be contracted in the rotating direction between the first member and the second member.
In a torque detector according to a ninth aspect, the torque detector of the eighth aspect is configured so that initial torque is applied to the elastic member. In this torque detector, the elastic member is not contracted in the rotating direction until torsional torque exceeds the initial torque of the elastic member. In other words, the first member and the second member rotate together and frictional resistance is not generated between both the members until that time. As a result, the second torque sensor can accurately detect minute torque.
These and other objects, features, aspects and advantages of the present invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses a preferred embodiment of the present invention.